Study On Thermoelectric Properties Of Chalcogenides

With the rapid development of industrial civilization and society,energy shortage and environmental pollution have become two major problems that we have to face and solve.So,the increasing demand for green and clean energy has promoted the exploration of new energy sources,among which thermoelectric conversion technology have become a very promising solution.As an advanced new functional material,thermoelectric material has the ability to directly convert heat into electric energy.Thermoelectric devices made of this material have the advantages of environmental protection,long service life,good stability and so on.At present,many kinds of thermoelectric materials have been discovered,among which chalcogenides are a kind of thermoelectric materials with relatively low cost,friendly environment and relatively stable thermoelectric properties.Cu₃SbSe₃ and AgSbSe₂ are two models of chalcogenides,having intrinsic low thermal conductivity because of special structure,composed of elements with low toxicity and abundant on earth,so they are a kind of medium temperature thermoelectric materials with great application potential.However,compared with other traditional thermoelectric materials in the medium temperature region,their properties still have some shortcomings.The research purpose of this paper is to improve the thermoelectric properties of Cu₃SbSe₃ and AgSbSe₂.The obtained main results are given in the following:(1)We studied the thermoelectric properties of Ge doped Cu₃SbSe₃.The results show that the Ge-doping can maintain the power factor of the matrix while reducing the thermal conductivity.Finally,the sample of Cu₃Sb_0.96Ge_0.04Se₃ reached the ZT value of 0.32 at 673K,which is 28%higher than that the matrix of undoped,indicating that Ge element doping can effectively improve its thermoelectric properties.(2)We studied the influence of Cd doping on the thermoelectric performance of AgSbSe₂,and the results show that the substitution of Cd⁺²for Sb⁺³significantly improves the conductivity,resulting in greatly increase in the power factor and thus greatly improving the thermoelectric properties of AgSbSe₂material.Finally,the sample of AgSb_0.97Cd_0.03Se₂reached the highest ZT value of 0.88 at 623 K,which is about 293%higher than that of the sample without Cd-doping.This indicates that Cd doping is an effective means to improve the thermoelectric properties of AgSbSe₂material.(3)We also investigated the thermoelectric properties of Zn doped AgSbSe₂materials.The experimental results show that that the second phase of Agnanoparticles precipitates during the preparation of the sample of AgSb_0.96Zn_0.04Se₂,which leads to the generation of Agvacancy and further enhances the conductivity of the sample,and the presence of the second phase also enhances the phonon scattering.Finally,excellent thermoelectric properties were obtained in this sample,and the ZT value reached 1.12 at 673 K,which was 4.48 times higher than that of AgSbSe₂.This value was second only to the best Bi doping and Pb doping recently made in this system,indicating that Zn doping is a very effective means to improve the thermoelectric properties of AgSbSe₂ material.